CN108069497B

CN108069497B - Method for treating organic wastewater by catalytic wet oxidation

Info

Publication number: CN108069497B
Application number: CN201610991591.2A
Authority: CN
Inventors: 赵越; 蒋广安; 李宝忠; 张晔; 刘忠生
Original assignee: China Petroleum and Chemical Corp; Sinopec Fushun Research Institute of Petroleum and Petrochemicals
Current assignee: China Petroleum and Chemical Corp; Sinopec Fushun Research Institute of Petroleum and Petrochemicals
Priority date: 2016-11-11
Filing date: 2016-11-11
Publication date: 2021-07-09
Anticipated expiration: 2036-11-11
Also published as: CN108069497A

Abstract

The invention relates to the technical field of wastewater treatment, and particularly discloses a method for treating organic wastewater by catalytic wet oxidation, which comprises the following steps: and the organic wastewater and an oxidant enter a reactor to react, and a catalyst A and a catalyst B are sequentially filled in the reactor according to the contact sequence of the organic wastewater and the oxidant. The method has simple process and good stability, not only has high COD removal capability, but also can solve the problem of metal loss.

Description

Method for treating organic wastewater by catalytic wet oxidation

Technical Field

The invention relates to the field of environmental protection, in particular to a method for treating organic wastewater.

Background

The large amount of organic polluted wastewater caused by industrial production seriously affects the living state and ecological environment of human beings, and becomes an increasingly serious social and economic problem, and especially the organic wastewater which is difficult to biodegrade is more difficult to treat; in addition, because water resources are increasingly in short supply, the national control on the total emission amount of pollutants in water is increasingly strict, the formulation of new standards provides new challenges for the prevention and treatment work of water pollution of refining and chemical enterprises in China, and after the refining and chemical enterprises use the existing secondary biochemical process for treatment, most of discharged wastewater and sewage cannot meet the emission requirements of the new standards. Therefore, the external sewage needs to be deeply treated to achieve standard discharge and even can be recycled, which is of great significance in reducing the discharge amount of discharged pollutants of the wastewater, reducing the pollution discharge cost of enterprises, reducing the consumption of water resources and the like.

The wet catalytic oxidation method is an advanced treatment technology of high-concentration organic wastewater developed by adding a catalyst on the basis of a wet air oxidation method, and under the conditions of a certain temperature (160-280 ℃) and pressure (2-9 MPa), in a reactor filled with a special catalyst, oxygen-enriched gas or oxygen is used as an oxidant to catalyze and degrade pollutants such as COD (chemical oxygen demand), TOC (Total organic carbon), ammonia nitrogen and the like in the high-concentration organic wastewater to convert the pollutants into CO₂、N₂And water and other harmless components to reach the aim of purifying water quality. The wet catalytic oxidation method can achieve higher treatment efficiency under milder operating conditions than the air oxidation method, thereby greatly reducing investment and operation costs, and is considered to be a wastewater treatment technology with wide industrial application prospects. The difficulty with this technique is the catalyst. At present, the research on the catalyst at home and abroad mainly comprises two types of noble metal catalysts and non-noble metal catalysts. Japanese patent focuses mainly on the noble metal active group supported on TiO₂Or TiO₂-ZrO₂The above. Noble metal catalysts have high activity and high stability, but are expensive. The non-noble metal catalyst mainly comprises oxides and composite oxides of metals such as iron, copper, manganese and the like, wherein the copper catalyst has good catalytic action because oxygen on the surface of copper oxide is easy to lose, but copper ions are easy to lose in wastewater to cause secondary pollution, the content of total copper in the primary standard of national restriction (GB 8978-1996) sewage discharge is lower than 500 mu g/L, and the requirement of the secondary standard is lower than 1000 mu g/L.

Patent CN01135047.4 discloses a preparation and application of a copper-based catalyst for catalytic wet oxidation treatment of industrial wastewater. The main components of the catalyst are copper, zinc, nickel, magnesium, aluminum, chromium, iron and a part of rare earth metal oxides. The catalyst is prepared by coprecipitation of salts containing various metals to obtain a catalyst with a hydrotalcite-like structure, so that the loss of copper ions is controlled. However, the catalyst has obvious effect only in a system of phenol, sodium dodecyl benzene sulfonate and salicylic acid, and is greatly limited in application.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for treating organic wastewater by adopting catalytic wet oxidation, which has the advantages of simple process, good stability, high COD removal capacity and capability of solving the problem of metal loss.

The invention provides a method for treating organic wastewater by catalytic wet oxidation, which comprises the following steps: the organic wastewater and an oxidant enter a reactor to react, and a catalyst A and a catalyst B are sequentially filled in the reactor according to the contact sequence of the organic wastewater and the catalyst A, wherein the catalyst A is a noble metal supported catalyst, and the catalyst B is a copper-based supported catalyst.

In the method, the volume ratio of the catalyst A to the catalyst B is 20-80%: 20% to 80%, preferably 40% to 70%: 30 to 60 percent.

According to the method, an activated carbon bed layer is filled in the reactor, a catalyst A, a catalyst B and the activated carbon bed layer are sequentially filled in the reactor according to the contact sequence of the activated carbon bed layer and the organic wastewater, and the volume ratio of the catalyst A to the catalyst B to the activated carbon bed layer is 10-40%: 20% -70%: 20% -40%; preferably 20% to 30%: 40% -60%: 20 to 30 percent.

In the method, the catalyst A is a noble metal supported catalyst and comprises a carrier and an active metal component loaded on the carrier, wherein one or more of active carbon, a molecular sieve and an oxide are used as the carrier, the molecular sieve is one or more of A-type, Y-type, Beta, ZSM-5, TS-1 and MCM-41 molecular sieves, and the oxide is one or more of alumina, cerium dioxide, zirconium dioxide, titanium dioxide and silicon dioxide. One or more of noble metals of Pt, Pd, Rh, Ru and Ir are used as active metal components, and the content of the noble metals is 0.01-5.0 percent calculated by elements on the basis of the weight of the catalyst. The active metal component of the catalyst A comprises an auxiliary agent component, wherein the auxiliary agent component is rare earth metal, and the content of the rare earth metal is 0.1-20.0% by element. The rare earth metal is one or more of lanthanum, cerium, praseodymium and neodymium.

In the method, the catalyst B is a copper-based supported catalyst, comprises a carrier and an active metal component loaded on the carrier, and comprises the carrier and the active metal component loaded on the carrier, wherein one or more of active carbon, a molecular sieve and an oxide are used as the carrier; the molecular sieve is one or more of A-type, Y-type, Beta, ZSM-5, TS-1 and MCM-41 molecular sieves, and the oxide is one or more of alumina, cerium dioxide, zirconium dioxide, titanium dioxide and silicon dioxide; taking copper as an active metal component and rare earth metal as an auxiliary agent, and taking the weight of the catalyst as a reference, wherein the active metal component is calculated by the content of an oxide: CuO accounts for 1-30 wt%; the rare earth metal oxide is 0.1-25 wt%. The active metal component of the copper-based supported catalyst can also comprise one or more of iron, nickel or vanadium.

In the method, the rare earth metal is one or more of lanthanum, cerium, praseodymium and neodymium.

In the method, the reactor is also filled with an activated carbon bed layer, the activated carbon can be selected from conventional activated carbon commodities, and the specific surface area is 500-3000 m²A pore volume of 0.2-1.8 cm³(ii)/g, the average pore diameter is 1 to 10 nm.

In the method, the reaction temperature in the reactor is 120-350 ℃, and preferably 180-260 ℃; the reaction pressure is 1 to 8MPa, preferably 2 to 5 MPa.

In the method, the retention time of the organic wastewater in the catalyst bed layer is 10-300 minutes.

In the method of the invention, the oxidant is air, oxygen or hydrogen peroxide.

In the method, the dosage of the oxidant is 1.0-2.0 times of the dosage of the oxidant required by calculation according to the COD value of the original organic wastewater.

In the method, the COD of the organic wastewater is 500-300000 mg/L, and the wastewater can be any one or more of dye wastewater, petrochemical wastewater, coal chemical wastewater, pesticide wastewater and municipal wastewater.

The organic wastewater treatment method comprises the steps that wastewater is firstly contacted with a noble metal catalyst in the presence of an oxidant, and the oxidant converts a part of organic pollutants under the action of the noble metal catalyst and then is contacted with a copper catalyst with strong catalytic ability, so that the catalytic action of the copper catalyst is fully exerted; through the synergistic effect of the noble metal catalyst and the copper catalyst, the organic wastewater treatment effect is good, the loss of metal copper can be effectively reduced, and the problem of serious copper metal loss in the prior art in which the copper catalyst is used is solved. The downstream active carbon bed layer has the adsorption function of adsorbing organic pollutants and metal ions, can further remove the organic pollutants, and adsorbs the metal ions lost in the upstream reaction, thereby playing a dual role. Compared with the prior art, the method maintains higher COD removal effect of the organic wastewater by adopting a catalyst grading method, reduces the discharge of metal ions, has higher reaction activity and use stability, and is particularly suitable for catalytic wet oxidation reaction. The method has simple and convenient process, is easy to operate and is suitable for industrial application.

Detailed Description

The preparation process of the present invention is further illustrated below with reference to specific examples, but the scope of the present invention is not limited to these examples.

Preparation of catalyst A1 (Ru/AC)

The diameter of the mixture is 2.0mm, the specific surface area is 704m²G, pore volume 0.7cm³Per gram, commercial cylindrical activated carbon strips with an average pore size of 2.0 nm were dried at 120 ℃ for future use. Weighing 500g of dried activated carbon strips, and using RuCl according to the water absorption rate of the activated carbon strips₃The solution is prepared according to the proportion that Ru accounts for 2 percent of the total weight of the catalyst. Soaking the activated carbon strip with Ru solution for 24 hours in the same volume, drying at 100 ℃, putting the dried activated carbon strip into a tube furnace, and soaking the activated carbon strip with 10% H at 400 DEG C₂N of (A)₂Reducing for 4 hours, and then using the catalyst containing 1% of O₂N of (A)₂After deactivation for 4 hours, the temperature was lowered to room temperature and taken out to obtain catalyst A1.

Preparation of catalyst A2 (Ru-Ce/Al)₂O₃）

Kneading macroporous alumina powder and peptizing agent, rolling, extruding to obtain clover-shaped carrier with diameter of 2.5mm, and baking at 550 deg.C in airAl is obtained after firing₂O₃Support, specific surface area 220 m²G, pore volume 0.7cm³G, average pore diameter of 10.4 nm. Taking a certain amount of RuCl according to the proportion of Ru accounting for 1.0%₃Solution, equivalent volume impregnation of the support for 24 hours. Drying at 120 deg.C, placing into a tube furnace, and heating at 400 deg.C with 10% H₂N of (A)₂Reducing for 4 hours, and then using the catalyst containing 1% of O₂N of (A)₂And passivating for 4 hours. Then weighing a certain amount of Ce (NO) according to the proportion that Ce accounts for 5.0 percent₃)₃·6H₂And O, preparing a solution, and soaking the sample prepared in the previous step in an equal volume for 24 hours. Drying at 120 deg.C, placing into a tube furnace, roasting with nitrogen gas at 800 deg.C for 4 hr, and then using a furnace containing 1% O₂N of (A)₂And passivating for 4 hours. The temperature was lowered to room temperature and taken out to obtain catalyst A2.

Preparation of catalyst B1 (Cu-Ce/AC)

The diameter of the mixture is 2.0mm, the specific surface area is 704m²G, pore volume 0.7cm³Per gram, commercial cylindrical activated carbon strips with an average pore size of 2.0 nm were dried at 120 ℃ for future use. 500g of dried activated carbon strips are weighed and Cu (NO) is used according to the water absorption rate₃)₂·3H₂O and Ce (NO)₃)₃·6H₂O as CuO and CeO₂The catalyst is prepared into solution according to the proportion of 6 percent and 2 percent of the total weight of the catalyst respectively. And (3) soaking the activated carbon strip with Cu-Ce solution in the same volume for 2 hours, drying at 80 ℃, roasting at 550 ℃ for 4 hours in a nitrogen atmosphere, cooling to room temperature, and taking out to obtain the catalyst B1.

Preparation of catalyst B2 (Cu-Fe-Ce/ZSM-5)

The diameter of the mixture is 2.0mm, the specific surface area is 320m²G, pore volume 0.3 cm³The commercial ZSM-5 molecular sieve strip carrier with the average pore diameter of 2.4nm is dried at 120 ℃ for standby. Weighing 500g of ZSM-5 molecular sieve carrier and using Cu (NO)₃)₂·3H₂O、Fe(NO₃)₃·9H₂O and Ce (NO)₃)₃·6H₂O as CuO, Fe₂O₃And CeO₂The catalyst is prepared into 1000 mL solution according to the proportion of 6 percent, 2 percent and 1 percent of the total weight of the catalyst respectively. Impregnating ZSM-5 carrier with Cu-Fe-Ce solution, stirring in constant temperature water bath at 60 deg.C for 3 hr, standing in air for 24 hr, and rotary steamingDrying the hair bulb at 80 ℃ in vacuum and drying the obtained sample in a drying box at 100 ℃. Then, the catalyst was calcined at 550 ℃ for 4 hours in a muffle furnace, and the temperature was lowered to room temperature and taken out to obtain catalyst B2.

The activated carbon has a diameter of 2.0mm and a specific surface area of 704m²G, pore volume 0.7cm³A commercial activated carbon in the form of a column having an average pore diameter of 2.0 nm, dried at 120 ℃ for use.

Example 1

Catalysts A1 and B1 were loaded in a cylindrical reactor in proportions of 60% and 40% by volume, respectively, with a total volume of 100cm³. The used wastewater is refinery wastewater, the COD initial value is 4620.7 mg/L, oxygen is used as an oxidant, and the dosage is 1.6 times of the required theoretical value. The temperature of the reactor is 260 ℃, the pressure is 3.5 MPa, and the retention time is 60 minutes. The liquid after the reaction was tested for its COD and the catalyst activity was measured as the removal rate of COD. After the reaction, the liquid is tested for the content of copper ions by inductively coupled plasma mass spectrometry (ICP-MS) to examine the loss condition of the metal. The results are shown in Table 1.

Example 2

The catalysts A2 and B1 were charged into the reactor in proportions of 20% and 80% by volume, respectively, and the flow rate of the waste water was adjusted so that the residence time in the catalyst bed was 12 minutes, the amount of oxygen was 2.0 times the theoretical value required, and the other reaction conditions were the same as in example 1. The results are shown in Table 1.

Example 3

Catalysts A1 and B2 were charged into the reactor in proportions of 80% and 20% by volume, respectively, and the flow of the waste water was adjusted so that the residence time in the catalyst bed was 240 minutes, the amount of oxygen was 1.2 times the theoretical value required, and the other reaction conditions were the same as in example 1. The results are shown in Table 1.

Example 4

Catalysts A1, B1 and activated carbon were charged into the reactor in proportions of 30%, 50% and 20% by volume, respectively, under the same reaction conditions as in example 1. The results are shown in Table 1.

Example 5

The catalysts A2, B1 and activated carbon were charged into the reactor in the proportions of 10%, 50% and 40% by volume, respectively, and the flow rate of the wastewater was adjusted so that the residence time in the catalyst bed was 120 minutes, and the other reaction conditions were the same as in example 1. The results are shown in Table 1.

Example 6

The catalysts A1, B2 and activated carbon were charged into the reactor in proportions of 40%, 40% and 20% by volume, respectively, and the flow rate of the wastewater was adjusted so that the residence time in the catalyst bed was 20 minutes, and the other reaction conditions were the same as in example 1. The results are shown in Table 1.

Table 1 comparison of results from examples 1-6

Example 7

The reaction conditions were the same as in example 4, the waste water model compound used was phenol, the COD of the original solution was 3247.6 mg/L, the reaction temperature was 210 ℃ and the pressure was 2.5 MPa. The results are shown in Table 2.

Example 8

The reaction conditions were the same as in example 4, the used wastewater model compound was methylene blue, the COD of the original solution was 5326.7 mg/L, the reaction temperature was 220 ℃, the pressure was 3.2 MPa, air was used as the oxidant, and the amount was 1.6 times the theoretical value. The results are shown in Table 2.

Example 9

The reaction conditions are the same as example 4, the used wastewater is coal chemical wastewater, the COD of the original solution is 7381.5 mg/L, the reaction temperature is 220 ℃, the pressure is 3.0 MPa, the hydrogen peroxide is used as an oxidant, and the dosage is 1.2 times of the required theoretical value. The results are shown in Table 2.

Table 2 comparison of results for examples 7-9

Comparative example 1

Catalyst A1 was used alone and the reaction conditions were the same as in example 1. The results are shown in Table 3.

Comparative example 2

Catalyst B1 was used alone and the reaction conditions were the same as in example 1. The results are shown in Table 3.

Comparative example 3

Catalyst B1 and activated carbon were charged to the reactor in proportions of 60% and 40% by volume, respectively, under the same reaction conditions as in example 1. The results are shown in Table 3.

Comparative example 4

Catalyst B2 and activated carbon were charged to the reactor in proportions of 60% and 40% by volume, respectively, under the same reaction conditions as in example 1. The results are shown in Table 3.

TABLE 3 comparison of results of comparative examples 1-4

From the above examples and comparative examples it can be seen that: the catalyst grading mode of the invention can obviously reduce the loss of copper ions and simultaneously keep higher COD removal rate.

Claims

1. A method of catalytic wet oxidation treatment of organic wastewater, the treatment method comprising: the organic wastewater and an oxidant enter a reactor to react, and a catalyst A, a catalyst B and an active carbon bed layer are sequentially filled in the reactor according to the contact sequence of the organic wastewater and the catalyst A, wherein the catalyst A is a noble metal supported catalyst and comprises a carrier and an active metal component supported on the carrier, and one or more of active carbon, a molecular sieve and an oxide are used as the carrier; the catalyst B is a copper-based supported catalyst, which comprises a carrier and an active metal component loaded on the carrier, wherein one or more of active carbon, a molecular sieve and an oxide are used as the carrier.

2. The method of claim 1, wherein: the volume ratio of the catalyst A to the catalyst B to the activated carbon bed layer is 10-40%: 20% -70%: 20% -40%.

3. The method of claim 1, wherein: the volume ratio of the catalyst A to the catalyst B to the activated carbon bed layer is 20-30%: 40% -60%: 20 to 30 percent.

4. The method of claim 1, wherein: the catalyst A is a noble metal supported catalyst, the molecular sieve is one or more of A-type, Y-type, Beta, ZSM-5, TS-1 and MCM-41 molecular sieves, and the oxide is one or more of alumina, cerium dioxide, zirconium dioxide, titanium dioxide and silicon dioxide; one or more of noble metals of Pt, Pd, Rh, Ru and Ir are used as active metal components, and the content of the noble metals is 0.01-5.0 percent calculated by elements on the basis of the weight of the catalyst.

5. The method of claim 4, wherein: the active metal component of the catalyst A comprises an auxiliary agent component, wherein the auxiliary agent component is rare earth metal, and the content of the rare earth metal is 0.1-20.0% by element.

6. The method of claim 5, wherein: the rare earth metal is one or more of lanthanum, cerium, praseodymium and neodymium.

7. The method of claim 1, wherein: the catalyst B comprises a carrier and an active metal component loaded on the carrier, the molecular sieve is one or more of A-type, Y-type, Beta, ZSM-5, TS-1 and MCM-41 molecular sieves, and the oxide is one or more of alumina, cerium dioxide, zirconium dioxide, titanium dioxide and silicon dioxide; taking copper as an active metal component and rare earth metal as an auxiliary agent, and taking the weight of the catalyst as a reference, wherein the active metal component is calculated by the content of an oxide: CuO accounts for 1-30 wt%; the rare earth metal oxide is 0.1-25 wt%.

8. The method of claim 7, wherein: the active metal component of the catalyst B comprises one or more of iron, nickel or vanadium.

9. The method of claim 7, wherein: the rare earth metal is one or more of lanthanum, cerium, praseodymium and neodymium.

10. The method of claim 1, wherein: the specific surface area of the activated carbon bed layer filled in the reactor is 500-3000 m²A pore volume of 0.2-1.8 cm³(ii)/g, the average pore diameter is 1 to 10 nm.

11. The method of claim 1, wherein: the reaction temperature in the reactor is 120-350 ℃, and the reaction pressure is 1-8 MPa.

12. A method according to claim 1 or 11, characterized by: the reaction temperature in the reactor is 180-260 ℃; the reaction pressure is 2-5 MPa.

13. The method of claim 1, wherein: the retention time of the organic wastewater in the catalyst bed layer is 10-300 minutes.

14. The method of claim 1, wherein: the oxidant is air, oxygen or hydrogen peroxide.

15. The method of claim 1, wherein: the dosage of the oxidant is 1.0-2.0 times of the dosage of the oxidant calculated according to the COD value of the raw material organic wastewater.

16. The method of claim 1, wherein: the COD of the organic wastewater is 500-300000 mg/L.

17. The method of claim 1, wherein: the organic wastewater is one or more of dye wastewater, petrochemical wastewater, coal chemical wastewater, pesticide wastewater and municipal wastewater.